Antibiotics are rare medical supplies that have a 4.76% chance of spawning in Hospitals and medical tents, and a 0.98% of spawning in any other loot spawn in including Deer Stands, Churches and Supermarkets. They have a very small chance of dropping on Zombie Soldier (Heavy)s.

Antibiotics are the only item in the game that can cure infection and can be used immediately without an animation unlike bandaging or injecting morphine. Resting at a tent has a 1% chance of curing infection, but can only be done once per five minutes.

A player has a small chance of getting infected when hit by a zombie while they are bleeding, when staying near an already infected player, or while the player's Temperature is below 34°C, or otherwise very low. New 'viral' zombies have a high chance of causing an infection when they attack and hit the player.

An infected player loses blood continuously, but slowly, until they die. The blood level indicator (blood drop) on the Heads-Up Display (HUD) will have a sickly looking outline around it to show that the player has an infection, and a downwards facing arrow will indicate slow but continuous blood loss. The journal (assign key: Action 20) will note that the player feels "really sick."

There are preventive methods to help prevent infection in a player. These include keeping body temperature in the 'safe' range, this can be determined when the temperature icon on the HUD is red. Staying near a Fireplace, using Heatpacks or going indoors to raise temperature and keep it in the 'safe' range. Also, stay away from players showing symptoms of infection, such as coughing.

It is inferred that the infection that created the zombies is a viral pathogen. In reality, antibiotics are only effective against bacterial infections. However, the Antibiotics in DayZ can still cure an infection caused by a Zombie bite or environmental stress (low body temperature).